The use of shock waves in the medical community is not new. Early approaches of using shock waves for medical treatment required immersing the patient in water and directing a shock wave, generated by an underwater spark discharge, at a solid site to be treated, such as a bone or kidney stone. When the shock wave hits the solid site, a liberation of energy from the change of acoustic impedance from water to the solid site produces pressure in the immediate vicinity of the site. For example, U.S. Pat. No. 4,905,671 to Senge et al., issued on Mar. 6, 1990, teaches a method applying acoustic shock waves to induce bone formation. Senge et al. utilizes the extremely short rise time of the shock wave to create high compression zones within bone tissue to cause reactions of the microcompartments of the bone. Senge et al. purports that such reactions cause the formation of hematomas within bone, which in turn, induce the formation of new bone.
Senge et al. utilizes a shock wave source consisting of a spark gap between electrodes within a container of water. An electrical condenser connected to the electrodes releases its energy over a very short period of time, and an arc arises between the electrodes of the spark gap device which vaporizes water surrounding the path of the spark, thereby establishing a plasma-like state. The result is an explosion-like vaporization of the water, which produces an electro-hydraulic shock wave that spreads out in a circular fashion. A metallic, ellipsoid-shaped structure surrounds a rear portion of the spark gap, opposite the patient, to produce a focal point of the shock wave that coincides with a location in the pathological bone site at which the shock wave is to be focused. The size and shape of the ellipsoid dictate the position of the focal point. This device also requires that the patient be submerged in the water.
U.S. Pat. No. 4,979,501 to Valchanov et al., issued on Dec. 25, 1990, teaches a method and apparatus for treating pathologies with shock or “impact” waves for correction of delayed bone consolidation and bone deformations. The method comprises the steps of anesthetizing the patient, fixing the limb affected with the pathological bone condition, centering the pathological site of the bone on the shock wave focal point, treating the affected bone site once or consecutively, with 300 to 6000 impacts. The impacts have a frequency of 0.4–4.0 per second with a pulse duration of 0.5 to 4.0 microseconds for a period of 10–120 minutes. After these steps have been performed, the limb is immobilized for a period from 15 to 90 days.
The impact wave-generating device disclosed by Valchanov et al. generally consists of a vessel that contains a transmitting medium or acoustic liquid such as water. At a bottom portion of the vessel, opposed electrodes are disposed, which are adapted to produce a shock across the gap. Therefore, the patient is not submerged for treatment.
U.S. Pat. No. 4,896,673 to Rose et al., teaches a method and apparatus that utilize focused shock wave treatment of kidney stones in combination with localization using ultrasound or x-ray imaging. Rose et al. discloses that if the number and magnitude of the shock wave pulses are sufficient, the shock wave treatment may disintegrate a kidney stone.
Shock waves have also been used to treat soft tissue. For example, U.S. Pat. No. 5,316,000 to Chapelon et al. discloses an array of composite piezoelectric transducers for making an acoustic or ultrasonic therapy device for use in the treatment of varicose veins. U.S. Pat. No. 5,458,130 to Kaufman et al. discloses using shock waves to treat soft tissue such as cartilage, ligament, and tendons.
To date, shock waves have not been used in the medical field of orthodontics. Standard orthodontics for the treatment of malocclusion may typically require 18–30 months to complete, depending on the severity of the problem. Generally, orthodontic patients are anxious to finish their treatment in as short a period of time as possible. In an effort to speed up orthodontic treatment, surgical techniques have been expanded over recent decades. The most recent and most refined of these techniques has been presented by William and Thomas Wilcko, as Accelerated Osteogenic Orthodontics (AOO), and involves peeling back the gingival tissue from the cortical bone surrounding the teeth and then performing corticotomy. Corticotomy is a procedure that barely cuts through the cortical bone between the teeth with a rotary instrument. After the cuts have been made, certain bone augmentation procedures are performed to speed up the orthodontic treatment. The gingival flap is then replaced.
AOO causes a tissue metabolic process to be initiated, which is referred to as regional accelerated phenomenon (RAP). RAP creates an increase in bone remodeling that starts as a drastic demineralization of both medullary and cortical alveolar bone. Because the medullary bone has a much higher surface-to-volume ratio, and because the teeth are surrounded primarily by medullary bone, RAP renders the bone around the teeth largely into demineralized osteoid, a condition known as osteopenia. When osteopenia has thusly been established around teeth, it has been shown that orthodontic appliances can be used that enable treatment to be completed in about ⅓ of the amount of time typically required to treat malocclusion. One of the drawbacks to AOO is that it requires an invasive surgical procedure to initiate RAP and ostoepenia, which involves peeling back the gingival tissue and cutting through the cortical bone.
It would be desirable to provide a way to accelerate orthodontic treatment to enable treatment of malocclusion to be established without having to subject the patient to invasive surgery, such as that associated with AOO, for example.